Wheelchair electrical control circuit

Abstract

The normally provided manually operable switch lever on an electrically drive wheelchair incorporates pairs of switch arms so that additional circuitry can be provided for interconnection with the normally provided left and right wheel drive motors. This additional circuitry comprises electrical resistances arranged to be connected across the motor leads by the manually operable switch when in an unactuated position for the particular motor in question. The provision of these resistances across the motor leads when the motors are unenergized results in absorption of back voltage spikes to thereby avoid burning out the switch means, dynamic braking when the motors acts as generators as a result of the wheelchair coasting, easier steering control when only one of the motors is energized to effect a turn, and permits the use of permanent magnet type d.c. motors for the left and right wheel drive motors.

I claim: 
     
       1. An electrical control circuit for a wheelchair including left and right d.c. wheel motors, battery means and manually operable switch means for energizing the motors from the battery means, said circuit including, in combination: (a) a first resistance connected to shunt the negative and positive input leads of the right wheel motor when the portion of the switch means for energizing said right wheel motor is unactuated; and   (b) a second resistance connected to shunt the negative and positive input leads of the left wheel motor when the portion of the switch means for energizing said left wheel motor is unactuated whereby back voltage spikes generated when the motors are deenergized are absorbed in the resistances respectively to thereby protect the switch means against burn-out, dynamic braking is provided when the motors act as generators as a result of the wheelchair coasting, easier steering control is afforded when only one of the motors is energized to effect a turn and permanent magnet type d.c. motors can be utilized for said left and right wheel motors.   
     
     
       2. A control circuit according to claim 1, in which said switch means includes left forward, right forward, left rearward and right rearward pairs of switch arms, actuation of the left forward and right forward pairs of switch arms energizing said right and left wheel motors to drive the wheelchair forwardly, and actuation of the left rearward and right rearward pairs of switch arms reversing the polarity of the energy supplied by said battery means to said left and right wheel motors to reverse their rotational direction and drive the wheelchair rearwardly, said resistances being connected between neutral terminals engaged respectively by one of the switch arms of each pair when in unactuated positions. 
     
     
       3. A wheelchair electrical control circuit including, in combination: (a) a wheelchair having a left wheel drive motor and a right wheel drive motor;   (b) battery means for providing electrical energy to the motors carried on said wheelchair;   (c) manually operable switch means on said wheelchair including: (1) a vertically extending lever universally mounted for tilting movement in forward, rearward, leftward and rightward directions and diagonal directions therebetween generally in an horizontal plane; and,   (2) left forward, right forward, left rearward and right rearward pairs of switch arms positioned about said lever such that said left forward and right forward pairs of switch arms can be simultaneously actuated to close upon forward movement of said lever, said left rearward and right rearward pairs of switch arms can be simultaneously actuated to close upon rearward movement of said lever, said left forward and left rearward pairs of switch arms can be simultaneously actuated to close upon leftward movement of said lever and said right forward and right rearward pairs of switch arms can be simultaneously actuated to close upon rightward movement of said lever, and wherein any one of said pairs of switch arms can be actuated to close without the remaining pairs of switch arms being actuated by moving said lever in a diagonal direction directly towards the said one of said pairs; and     (d) circuit means interconnecting the switch means with the motors and battery means to drive said wheelchair, said circuit means including: (1) a first pair of leads connecting a first switch arm of the left forward pair of switch arms to a second switch arm of the right rearward pair of switch arms, and the second switch arm of the left forward pair of switch arms to the first switch arm of the right rearward pair of switch arms, respectively;   (2) a second pair of leads connecting a first switch arm of the right forward pair of switch arms to a second swith arm of the left rearward pair of switch arms, and a second switch arm in the right forward pair of switch arms to the first switch arm in the left rearward pair of switch arms, respectively;   (3) negative and positive left motor leads connected to the first and second switch arms of said left rearward pair of switch arms respectively;   (4) negative and positive right motor leads connected to the first and second switch arms of said right rearward pair of switch arms respectively;   (5) positive battery leads connecting to positive terminals positioned to be engaged by the first one of the respective pairs of switch arms when actuated by said lever;   (6) negative battery leads connecting to negative terminals positioned to be engaged by the second one of the respective pairs of switch arms when actuated by said lever, the first and second switch arms of each pair being ganged together for simultaneous movement;   (7) a first electrical resistance connected between first and second neutral terminals positioned to be engaged by the first switch arms of said left forward and right rearward pairs of switch arms when in unactuated position; and   (8) a second electrical resistance connected between third and fourth neutral terminals positioned to be engaged by the first switch arms of said right forward and left rearward pairs of switch arms when in unactuated position, whereby when said lever is in a central neutral position so that none of said switch arms is actuated, said first electrical resistance is connected between said negative and positive right motor leads and said second electrical resistance is connected between said negative and positive left motor leads so that back voltage spikes generated when the motors are de-energized are absorbed in the resistances respectively to thereby protect the switch means against burn-out, dynamic braking is provided when the motors act as generators as a result of the wheelchair coasting, easier steering control is afforded when only one of the motors is energized to effect a turn, and permanent magnet type d.c. motors can be utilized for said left and right wheel drive motors.       
     
     
       4. A wheelchair according to claim 3, in which said battery means includes two batteries each having positive and negative terminals; and fast-slow switch means interconnecting said positive and negative battery leads to said terminals when in a first position to electrically connect said batteries in series between said leads, and interconnecting said positive and negative battery leads to said terminals when in a second position to electrically connect said batteries in parallel between said leads.